V0 1889 n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 34H 



Genug CALLIOSTOMA Swainson. 



Calliostoma platinum sp. uov. 



Plate vii. Fig. -2. 



Shell large, thin, polished, iridescent white, with seven whorls beside 

 the nucleus; nucleus minute, lost; subsequent whorls slightly flattened 

 behind the periphery, full and rounded on the base; longitudinal sculp- 

 ture of obscure spiral lines behind the periphery and somewhat stronger 

 flattish threads, separated by shallow grooves, on the base; at the 

 periphery is a single prominent thread, immediately in front of which is 

 the suture, the succeeding whorl being appressed against the thread ; the 

 single specimen obtained has a second prominent thread about two 

 millimeters behind the peripheral one on the last whorl, but it is prob- 

 able that the development of this thread was stimulated by an injury 

 of which traces are plainly visible just before the second .thread begins ; 

 base full aud rounded; aperture rounded quadrate; the outer lip thin 

 and sharp, its plane oblique and slightly flexuous ; body with a very 

 faint wash of callus; pillar slender, pearly, slightly arched, very little 

 reflected, simple; interior polished, iridescent, without line; the exter- 

 nal sculpture faintly perceptible owing to the tenuity of the shell. 

 Maximum longitude of shell, 32; maximum latitude, 2!)""". 



Hab.— Station 2839, near the Santa Barbara Islands, California, 

 in 414 fathoms, sand; with Turcicula Bairdii. 



The operculum of this species has about fourteen very narrow whorls, 

 is polished internally and somewhat rough externally from the project- 

 ing margin of the coils. It bears about the same proportion to the 

 aperture as in the shallow water species. The shell itself is less at- 

 tractive than most of the group, but indicates that some individuals of 

 the species may have a delicate pale iridescence. The exterior of this 

 specimen, shows little pearliness and is chiefly of a somewhat livid 

 white, like the eye of a boiled fish. 



The soft parts are whitish ; the head and the sides of the foot below 

 theepipodial line are profusely granulose ; among the granules rise 

 pointed larger papillsB, also very granulose, so as to appear almost 

 arborescent. The epipodial line projects moderately, with a finely 

 fringed edge. There are two moderate sized filaments in front of the 

 operculum and two smaller ones beneath it. The foot is long, rather 

 narrow, double-edged, and somewhat auriculate in front, with a wide 

 transversely rugose median channel behind the operculum about the 

 tail. The oral surface is granulous, the corners area little produced. 

 The tentacles are long aud slender, the eyes very large and black. 

 There are uo palmettes. The gill resembles that of Turcicula, but is 

 less triangular as a whole. The mantle margin is finely papillose. The 

 jaws are small and not remarkable. The dentition was not examined. 



